With the advancement of the Internet, there is a grown interest in obtaining and maintaining user-related data. For example, data, e.g., age, gender, marital status, education, etc., regarding a user is requested by a social networking website from the user. Once the user provides the data, the data may be used for advertisement. As another example, a user's history of renting movies is stored in a database to estimate another movie that the user might want to rent. As another example, a user's purchase of products is maintained in a database to provide suggestions to the user to purchase other related products.
It is in this content that various embodiments described in the present disclosure arise.